Abstract
This paper investigates micromachined antenna performance operating at 5 GHz for radio frequency (RF) energy harvesting applications by comparing different substrate materials and fabrication modes. The research aims to discover appropriate antenna designs that can be integrated with the rectifier circuit and fabricated in a CMOS (Complementary Metal-Oxide Semiconductor)-compatible process approach. Therefore, the investigation involves the comparison of three different micromachined antenna substrate materials, including micromachined Si surface, micromachined Si bulk with air gaps, and micromachined glass-surface antenna, as well as conventional RT/Duroid-5880 (Rogers Corp., Chandler, AZ, USA)-based antenna as the reference. The characteristics of the antennas have been analysed using CST-MWS (CST MICROWAVE STUDIO®—High Frequency EM Simulation Tool). The results show that the Si-surface micromachined antenna does not meet the parameter requirement for RF antenna specification. However, by creating an air gap on the Si substrate using a micro-electromechanical system (MEMS) process, the antenna performance could be improved. On the other hand, the glass-based antenna presents a good S11 parameter, wide bandwidth, VSWR (Voltage Standing Wave Ratio) ≤ 2, omnidirectional radiation pattern and acceptable maximum gain of >5 dB. The measurement results on the fabricated glass-based antenna show good agreement with the simulation results. The study on the alternative antenna substrates and structures is especially useful for the development of integrated patch antennas for RF energy harvesting systems.
Highlights
In recent years, there has been a growing interest from both academia and industry in the deployment of energy capture of ambient energy for fully autonomous powering of microdevices, using different energy harvesting techniques
We investigate alternative concepts to replace the conventional antenna substrate, as well as different fabrication modes, in order to discover the optimal receiving antenna design for an radio frequency (RF) energy harvester system operating at 5 GHz in the unlicensed industrial, scientific and medical (ISM) band, which is chosen as it is a free RF signal source that receives from various radio wireless devices
The antenna characteristics were analyzed by comparing the effects of the substrate material and the structure manipulated through the surface and bulk micromachining processes
Summary
There has been a growing interest from both academia and industry in the deployment of energy capture of ambient energy for fully autonomous powering of microdevices, using different energy harvesting techniques. The micromachining process involves the selective removal of glass or Si substrate to produce an air cavity (εr = 1), which decreases the total εr of the substrate system [16,19]. In this project, we investigate alternative concepts to replace the conventional antenna substrate, as well as different fabrication modes, in order to discover the optimal receiving antenna design for an RF energy harvester system operating at 5 GHz in the unlicensed industrial, scientific and medical (ISM) band, which is chosen as it is a free RF signal source that receives from various radio wireless devices. The proposed antenna is appropriate to be integrated with the rectifier circuit in the RF energy harvesting system, and can be fabricated in a CMOS-compatible process method
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